What is a nuclear fission reaction ? Explain the principle of atomic bomb and working of a nuclear reactor to produce electricity.

Explanation

Nuclear fission reaction `:` The process of splitting ofa heavy nucleus into two nuclie of nearly comparable masses with the liberation of energy is called nuclear fission . A nuclear fission reaction may be represented by the equation `:`
`._(92)U^(235)+``._(0)n^(1) rarr ``._(56)Ba^(141)+``._(36)Kr^(92)+3``._(0)n^(1)+`Energy
The energy released was estimated to be `200 MeV`.
Principle of the atomic bomb `:` It is based upon the controlled nuclear chain reaction. Two or more pieces of fissionable material `(U-235 or Pt-239)`, each less than the critical mass, are brought together rapidly by means of a conventional explosive so that the sub`-` critical pieces come together to form a single piece exceeding the critical mass. A chain reaction will start releasing a large amount of energy.
Nuclear reactor to produce electricity `:` In nuclear power stations, the electricity is produced by the fission reaction of uranium `-235` . The fuel used in nuclear power plants is enriched uranium containing about `2-3%` of `U-235`.
A lamp of uranium`-235` is kept in a nuclear reactor and bombarded with neutrons in the presence of a moderator such as graphite, cadmium, or heavy water. A chain reaction of uranium fission starts which produces an extremely large amount of heat energy. This heat is used to convert water into steam in boilers. This steam then drives the turbined to generates electricity.